Funerals, headstones, flowers are all for the living the dead are dead.
Yes it would be nice for her children to maybe visit grandpa's grave and see the headstone but maybe they have never gone and never will.
One can honor a person's memory more by keeping their tradions alive and their kindness and good deeds alive. A headstone is something that the family might never see. But stories about grandpa's great chili recipe are priceless.
Each of us honors the ones we love in a different way.
My mom's entire family died in concentration camp. There is no headstone, no pictures, no knick knack, nothing yet the memory of their kindness and love my mom told me about lives on.
If you visit your parents grave often it will be important to you but to many people they never visit, they keep the memories alive in different ways.